Loud pop/screech when powering on amp

if it is a blown cap, why would the amp still play and sound fine?

Sorry, OP; I don't know enough about electrical theory and function to answer that--I only know how to change parts assuming I can identify the correct ones.

I will say that I had an old preamp that was spitting and popping (but it did play) and I was talking to the tech at Cary about it (this was back when they would talk to you on the phone) and he actually did mention the possibility of a cap being bad.  So I guess it is possible that a cap could be on the way out but not completely gone?  I don't know for sure on that, and in the case of that preamp I just alluded to, it was actually some ancient worn out tubes.

@kingbr -- I hope you find out the issue, but if I were in your shoes, I would NOT continue to risk my SF Sonetto's.  For goodness sakes, disconnect those speakers ASAP.  If you want to continue to experiment with possible issues, connect the cheapest pieces of crap you can buy tomorrow off of Craigslist.  I've seen permanent damage done to high end speakers due to an ongoing sudden "pop" from the amp.  It baffles me that some brands accept a "power on pop" as normal or OK.  I'm not an electrical engineer expert or speaker driver manufacturer, but that sudden "pop" can't be good...it just can't.  Just my two cents worth.  Keep us updated!

@kingbr 

Fidelis Audio is in Nashua and is an excellent bricks and mortar audio store.  For a small processing fee they will pass the amp along for repair to Jim Fuller whose shop is Fuller Sound out of Waltham, MA.

I just used Jim to update the caps on my speakers and am quite happy with the upgrade.  But it's an old amp and cost may or may not be prohibitive.

Thanks so much for all the thoughtful replies!

@jetter I have bought from Fidelis Nice to know they can assist. To your point might be cost prohibitive.

@soix Thank you for the details on the McCormack. So tempted on that. I reached out to the seller to ask how old and if he’s the original owner…

So many things to think about??? And again maybe this is normal?? Joseph S of Earthquake flat out stated there will be a pop on startup. Still nothing from AR which is now Focal/Naim I guess. Stay put, have someone look at the AR, McCormack, or Outlaw???🤦🏼‍♂️🤷🏼‍♂️